Method and apparatus for tissue grafting

ABSTRACT

Exemplary embodiments of apparatus and method for harvesting small portions of tissue (“micrografts”) to form grafts can be provided. For example, a hollow tube can be inserted into tissue at a donor site, where a distal end of the hollow tube can have two or more points or extensions to facilitate separation of the micrografts from the surrounding tissue. The exemplary apparatus can be provided that includes a plurality of such tubes for simultaneous harvesting of a plurality of micrografts. The harvested micrografts can have a small dimension, e.g., less than about 1 mm, or less than about 0.3 mm, which can promote healing of the donor site and/or viability of the harvested tissue. The micrografts can be approximately cylindrical or strip-shaped, and can be placed in a biocompatible matrix to form a graft or directly into tissue at the recipient site. Such exemplary micrografts can be obtained from skin or other types of tissue, e.g., various internal organs.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from U.S. Provisional PatentApplication Ser. No. 61/041,587 filed Apr. 1, 2008, the disclosure ofwhich is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to exemplary embodiments of method andapparatus for providing tissue grafts using tissue from a donor site.

BACKGROUND INFORMATION

An autograft can refer to tissue transplanted from one part of anindividual's body (e.g., a “donor site”) to another part (e.g., a“recipient site”). Autografts can be used, for example, to replacemissing skin and other tissue and/or to accelerate healing resultingfrom trauma, wounds, burns, surgery and birth defects. Availability oftissue for autografting can be limited by characteristics of candidatedonor sites, including a number and/or total area of tissue grafts,healing behavior of the donor site, similarity of the donor andrecipient sites, aesthetic considerations, etc.

Skin grafting can be performed surgically. For example, a conventionalautograft procedure may include excision or surgical removal of burninjured tissue, choosing a donor site, which may be an area from whichhealthy skin is removed to be used as cover for the cleaned burned area,and harvesting, where the graft may be removed from the donor site,e.g., using an instrument similar to an electric shaver. Such instrument(e.g., a dermatome) can be structured to gently shave a piece of tissue,which may be, e.g., about 10/1000 of an inch thick for a split-thicknessgraft, from the skin at the unburned donor site to use as a skin graft.The skin graft can then be placed over the cleaned Wound so that it canheal. Donor skin tissue can be removed to such a depth that the donorsite can heal on its own, in a process similar to that of healing of asecond degree burn.

Two conventional types of autografts which may be used for a permanentwound coverage include sheet grafts and meshed grafts. A sheet graft canrefer to a piece of skin tissue removed from an undamaged donor site ofthe body, in a process that may be referred to as harvesting. The sizeof the donor skin piece that is used may be about the same size as thedamaged area. The sheet graft can be laid over the excised wound, andstapled or otherwise fastened in place. The donor skin tissue used insheet grafts may not stretch significantly, and a sheet graft can beobtained that is slightly larger than the damaged area to be coveredbecause there may often be a slight shrinkage of the graft tissue afterharvesting.

Sheet grafts can provide an improved appearance of the repaired tissuesite. For example, sheet grafts may be preferred for use on large areasof the face, neck and hands if they are damaged, so that these morevisible parts of the body can appear less scarred after healing. A sheetgraft may be used to cover an entire burned or damaged region of skin,e.g., if the damaged site is small. Small areas of a sheet graft can belost after placement because of a buildup of fluid (e.g., a hematoma)can occur under the sheet graft following placement the sheet graft.

Sheet grafts may be full-thickness or split-thickness. For example,split-thickness skin grafts can be used to cover wounds in burn and skinulcer patients. A conventional split-thickness graft can be formed,e.g., by harvesting a sheet of epidermis and upper dermal tissue from adonor site, in a procedure similar to that of peeling an apple. Thesplit-thickness graft can then be placed on the location of the burn orulcer. The skin tissue may then grow back at the donor site following agenerally extended healing time. Split-thickness grafts may bepreferable to full-thickness grafts because removing large amounts offull-thickness skin tissue from the donor site can lead to scarring andextensive healing times at the donor site, as well as an increased riskof infection. However, skin tissue removed from the donor site for asplit-thickness skin autograft can include only a thin epithelial layer,which can lack certain elements of the dermis that improve structuralstability and normal appearance in the recipient site.

Full-thickness skin grafts can be formed using sheets of tissue thatinclude the entire epidermis layer and a dermal component of variablethickness. Because the dermal component can be preserved infull-thickness grafts, more of the characteristics of normal skin can,be maintained following the grafting procedure. Full-thickness graftscan contain a greater collagen content, dermal vascular plexus, andepithelial appendages as compared to split-thickness grafts. However,full-thickness grafts can require more precise conditions for survivalbecause of the greater amount of tissue requiring revascularization.

Full-thickness skin grafts can be preferable for repairing, e.g.,visible areas of the face that may be inaccessible by local flaps, orfor graft procedures where local flaps are contraindicated. Suchfull-thickness skin grafts can retain more of the characteristics ofnormal skin including, e.g., color, texture, and thickness, as comparedto split-thickness grafts. Full-thickness grafts may also undergo lesscontraction while healing. These properties can be important on morevisible areas such as the face and hands. Additionally, full-thicknessgrafts in children can be more likely to grow with the individual.However, application of conventional full-thickness skin grafts can belimited to relatively small, uncontaminated, well-vascularized wounds,and thus may not be appropriate for as many types of graft procedures assplit-thickness grafts. Additionally, donor sites for full-thicknessgrafts can require surgical closure or resurfacing with asplit-thickness graft.

A meshed skin graft can be used to cover larger areas of open woundsthat may be difficult to cover using sheet grafts because of, e.g., alack of a sufficient area of healthy donor sites. Meshing of a skingraft can facilitate skin tissue from a donor site to be expanded tocover a larger area. It also can facilitate draining of blood and bodyfluids from under the skin grafts when they are placed on a wound, whichmy help prevent graft loss. The expansion ratio (e.g., a ratio of theunstretched graft area to the stretched graft area) of a meshed graftmay typically be between about 1:1 to 1:4. For example, donor skin canbe meshed at a ratio of about 1:1 or 1:2 ratio, whereas larger expansionratios may lead to a more fragile graft, scarring of the meshed graft asit heals, and/or extended healing times.

A conventional graft meshing procedure can include running the donorskin tissue through a machine that cuts slits through the tissue, whichcan facilitate the expansion in a pattern similar to that of fishnetting or a chain-link fence. Healing can occur as the spaces betweenthe mesh of the stretched graft, which may be referred to as gaps orinterstices, fill in with new epithelial skin growth. However, meshedgrafts may be less durable graft than sheet grafts, and a large mesh canlead to permanent scarring after the graft heals.

To help the graft heal and become secure, the area of the graft canpreferably not be moved for at least about five days following eachsurgery. During this immobilization period, blood vessels can grow fromunderlying tissue into the skin graft, and can help to bond the twotissue layers together. About five days after the graft is placed,exercise therapy programs, tub baths, and other normal daily activitiescan often be resumed. Deep second-degree and full-thickness burns mayrequire skin graft surgery for quick healing and minimal scarring. Largeburn sizes can lead to more than one grafting procedure during ahospital stay, and may require long periods of immobilization forhealing.

As an alternative to autografting, skin tissue obtained fromrecently-deceased people (which may be referred to, e.g. as a homograft,an allograft, or cadaver skin) can be used as a temporary cover for awound area that has been cleaned. Unmeshed cadaver skin can be put overthe excised wound and stapled in place. Post-operatively, the cadaverskin may be covered with a dressing. Wound coverage using cadavericallograft can then be removed prior to permanent autografting.

A xenograft or heterograft can refer to skin taken from one of a varietyof animals, for example, a pig. Heterograft skin tissue can also be usedfor temporary coverage of an excised wound prior to placement of a morepermanent autograft, and may be used because of a limited availabilityand/or high expense of human skin tissue. In some cases religious,financial, or cultural objections to the use of human cadaver skin mayalso be factors leading to use of a heterograft. Wound coverage using axenograft or an allograft is generally a temporary procedure which my beused until harvesting and placement of an autograft is feasible.

Epithelial appendages can preferably be regenerated following a graftingprocedure. For example, hair can be more likely to grow frontfull-thickness grafts than from split-thickness grafts, but such hairgrowth may be undesirable based on the location of the wound.Accordingly, donor sites for full-thickness grafts can be carefullyselected based in part, e.g., on patterns of hair growth at the time ofsurgery. Further, certain hair follicles may not be orientedperpendicular to the skin surface, and they can be transected if anincision provided to remove graft tissue is not oriented properly.

Sweat glands and sebaceous glands located in graft tissue may initiallydegenerate following grafting. These structures can be more likely toregenerate in full-thickness grafts than in split-thickness graftsbecause full-thickness grafts can be transferred as entire functionalunits. For example, sweat gland regeneration can depend in part onreinnervation of the skirt graft with recipient bed sympathetic nervefibers. Once such ingrowth has occurred, the skin graft can assume thesweating characteristics of the recipient site, rather than retainingthe characteristics of the donor site. In contrast, sebaceous glandregeneration may be independent of graft reinnervation and can retainthe characteristics of the donor site. Prior to the regeneration, theskin graft tissue may lack normal lubrication of sebum produced by theseglands, which can make such grafts more susceptible to injury.

In general, grafting procedures may be limited by the amount of tissuewhich can be removed from the donor site without causing excessiveadverse effects. Full-thickness grafts can provide improved tissuequality at the wound site, but the donor site may be more severelydisfigured as described above. Split-thickness grafts can be acompromise between healing times and aesthetic and functional propertiesof the donor and recipient sites, whereas meshing can provide moreextensive graft coverage at the expense of visible scarring.

Harvesting of graft tissue from the donor site generally can generateundesirable large-scale tissue damage to the donor site. On the otherhand, small areas of skirt wounding adjacent to healthy tissue can bewell-tolerated and my heal quickly. Such healing of small wounds canoccur in techniques such as “fractional photothermolysis” or “fractionalresurfacing,” in which patterns of damage having a small dimension canbe created in skin tissue. These exemplary techniques are described,e.g., in U.S. Pat. No. 6,997,923 and U.S. Patent Publication No.2006/0155266. Small-scale damage patterns can heal quickly by regrowthof healthy tissue, and can further provide desirable effects such asskin tightening without visible scarring.

In view of the shortcomings of the above described procedures for tissuegrafting, it may be desirable to provide exemplary embodiments of methodand apparatus that can provide tissue suitable for grafting whileminimizing unwanted damage to the donor sites.

SUMMARY OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present disclosure provide method andapparatus for obtaining small portions of graft tissue that can beaccompanied by rapid healing of the donor site. For example, theexemplary embodiment of the method can be provided for obtaining skingraft tissue by harvesting small portions of the tissue, e.g.,micrografts, from a donor site.

Such micrografts can comprise skin tissue that can include, e.g.,epidermal and dermal tissue, and/or tissue obtained from other bodyorgans. The micrografts can have at least one dimension that isrelatively small, e.g., less than about 1 mm, or less than about 0.5 mm,or optionally about 0.3 mm or less, or about 0.2 mm. Such exemplarysmall dimensions of the micrografts can facilitate both healing of thedonor site following harvesting and viability of the micrografts byallowing greater diffusional nourishment of the micrograft tissue. Thesmall regions of damage in the donor site caused by a removal of thetissue portions can heal rapidly with little or no formation of visiblescars. The micrografts obtained from skin tissue can include, e.g.,epidermal and dermal tissue, and can also include stem cells that can belocated proximal to the dermal/fatty layer boundary. The micrografts canalso be obtained from other types of tissue, e.g., various internalorgans or the like.

A fraction of dermal tissue that is removed from a donor site can be,e.g., less than about 70%, or less than about 50%, although otherfractions may be used. The harvested tissue portions can be in the shapeof cylinders, elongated strips, or other geometries which can include atleast one small dimension. In certain exemplary embodiments, a portionof the tissue at the donor site can be frozen or partially frozen. Suchfreezing can facilitate cutting, removal and/or viability of theharvested tissue portions.

An exemplary embodiment of the apparatus can be provided for harvestingmicrografts that can include a hollow tube. An inner diameter of thehollow tube can be approximately the same size as a diameter or width ofthe micrograft to be harvested. A distal end of the hollow tube can havetwo or more points to facilitate separation of the micrografts from thesurrounding tissue.

The micrografts can be harvested from the donor site by inserting theexemplary apparatus into tissue at the donor site to a particular depththereof, and then removing the tube. A stop cart be provided on the tubeto control or limit the depth of insertion of the tube. A slight suctionor pressure can be provided at a proximal end of the tube to facilitateharvesting of the micrografts and/or their removal from the tube.

A further exemplary embodiment of the apparatus can be provided thatincludes a plurality of such tubes for simultaneous harvesting of aplurality of micrografts. An enclosure and/or a source of pressure,e.g., a pump or the like, can be provided in communication with theproximal ends of the tubes to facilitate application of pressure and/orsuction to the plurality of tubes. A vibrating arrangement can becoupled to the apparatus to facilitate the insertion of the tubes intothe donor site.

The exemplary micrografts can be placed in a biocompatible matrix, e.g.,to form a graft or directly into tissue at the recipient site Thebiocompatible matrix can be formed using collagen, polylactic acid,hyaluronic acid, and/or other substances which can support the harvestedmicrograft tissue portions and promote their growth. The matrix canoptionally include, e.g., nutrients and/or other substances to promotetissue growth. The harvested tissue portions can be bonded to the matrixusing techniques such as photochemical tissue bonding to providestructural stability. The matrix can then be applied to the recipientsite, which can promote growth and revascularization of the tissueportions to form a continuous sheet of the grafted tissue.

The exemplary micrografts can also be gathered in a compactconfiguration to form graft tissue that can be applied directly to arecipient site. The exemplary micrografts can also be inserted directlyinto the tissue at a recipient site such as, e.g., scar tissue, using,e.g., the exemplary hollow tubes described herein.

These and other objects, features and advantages of the presentdisclosure will become apparent upon reading the following detaileddescription of exemplary embodiments of the present disclosure, whentaken in conjunction with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of the present disclosure willbecome apparent from the following detailed description taken inconjunction with the accompanying figures showing illustrativeembodiments, results and/or features of the exemplary embodiments of thepresent disclosure, in which:

FIG. 1A is a schematic illustration of an exemplary donor site aftercylindrical portions of micrograft tissue have been harvested therefrom;

FIG. 1B is a schematic illustration of the exemplary donor site shown inFIG. 1A after healing has occurred;

FIG. 1C is a schematic illustration of an exemplary micrograft that maybe removed from the exemplary donor site shown in FIG. 1A;

FIG. 2A is a cross-sectional view of an exemplary graft prepared byproviding harvested micrograft tissue portions in a biocompatiblematrix;

FIG. 2B is a is a cross-sectional view of the exemplary graft shown inFIG. 2A after it has been placed over a wound and some regrowth hasoccurred;

FIG. 3A is a schematic illustration of another exemplary donor siteafter elongated strips of tissue have been harvested therefrom;

FIG. 3B is a schematic illustration of the exemplary donor she shown inFIG. 3A after healing has occurred;

FIG. 3C is a schematic illustration of an exemplary tissue strip thatmay be removed from the donor site shown in FIG. 3A;

FIG. 4A is a schematic view in plan of a plurality of exemplarycylindrical micrograft tissue portions provided in a compact arrangementto form a graft;

FIG. 4B is a side view of the exemplary micrograft tissue portions shownin FIG. 4A;

FIG. 5A is a schematic illustration of an exemplary apparatus that canbe used to harvest micrograft tissue in accordance with first exemplaryembodiments of the present disclosure;

FIG. 5B is a schematic illustration of the exemplary apparatus that canbe used to harvest the micrograft tissue in accordance with secondexemplary embodiments of the present disclosure;

FIG. 6A is a schematic illustration of the exemplary apparatus shown inFIG. 5A that is inserted into an exemplary donor site to harvest anexemplary micrograft;

FIG. 6B is a schematic illustration of the exemplary apparatus shown inFIG. 5A that contains the harvested micrograft;

FIG. 6C is a schematic illustration of the exemplary apparatus shown inFIG. 5A showing the harvested micrograft being removed therefrom;

FIG. 7 is a schematic illustration of the exemplary apparatus that canbe used to harvest micrograft tissue in accordance with third exemplaryembodiments of the present disclosure;

FIG. 8A is an exemplary image of a distal end of the exemplary apparatusthat includes two points;

FIG. 8B is a further exemplary image of the distal end of the exemplaryapparatus shown in FIG. 7A; and

FIG. 9 is an exemplary image of the micrografts obtained using theexemplary apparatus shown in FIGS. 7-8B.

Throughout the drawings, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components, or portions of the illustrated embodiments. Moreover, whilethe present disclosure will now be described in detail with reference tothe figures, it is done so in connection with the illustrativeembodiments and is not limited by the particular embodiments illustratedin the figures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present disclosure provide methods andapparati for producing autografts, and particularly such methods aridapparati which can facilitate more rapid healing of the donor site whileproviding improved tissue characteristics at the recipient site.Exemplary embodiments of the present disclosure can include a pluralityof small-scale tissue portions (e.g., micrografts) that can be used toprovide autografts. Such micrografts can avoid significant permanentdamage to the donor site while providing graft tissue that can healrapidly and generate skin tissue having desirable properties at therecipient site.

In exemplary embodiments of the present disclosure, a method can beprovided for creating autografts in which tissue portions having atleast one small dimension (e.g., micrografts) are harvested from anexemplary donor site 100, as shown in FIG. 1A. The holes 110 shown inFIG. 1A represent regions of the exemplary donor site 100 from whichtissue portions (e.g., micrografts) have been removed. These exemplaryholes 110 may have art approximately round cross-sectional shape,although other shapes may be used.

The exemplary donor site 100 is shown in FIG. 1B after healing of theharvested tissue has occurred. The small regions of damage 100 createdat the donor site by the removed tissue can heal rapidly and/or withoutvisible scarring. For example, the residual pattern of the healed donorsite 100 shown in FIG. 1B may not be easily perceptible by the naked eyeunder normal viewing conditions.

An exemplary micrograft 120 that can be formed, e.g., by harvesting orremoving a portion of the tissue from the donor site 100 to form thehole 110 therein, is shown in FIG. 1C. The exemplary micrograft 120 canhave an elongated shape that may be approximately cylindrical. Themicrografts 120 can include both epidermal tissue 130 and dermal tissue140 from the exemplary donor site 100. For example, the exemplarymicrograft 120 can be about 3 mm in length, which can correspond to atypical total depth of the skin layer (e.g., epidermal and dermallayers). A different length my be used based on the particular skin ortissue characteristics of the donor site 100. In general, it can bepreferable to avoid harvesting a significant amount of subcutaneoustissue, so the harvested micrografts 200 can include primarily theepidermal tissue 130 and the dermal tissue 140. A lower portion 150 ofthe exemplary micrograft 120 can also include stern cells that can bepresent in a lower portion of the dermal layer of the donor site 100(e.g., near a dermal/fatty layer boundary).

A width or diameter of the holes 110 produced during harvesting (whichcan correspond approximately to the diameters of the portions of theharvested micrografts 120) can be less than about 1 mm, or less thanabout 0.5 mm. In certain exemplary embodiments, the diameter or widthcan be less than about 0.3 mm, or about 0.2 mm. The size of theexemplary holes 110 can be selected, e.g., based on the effects ofcreating small damage regions in the donor site 100 which can healrapidly and/or without scarring, and on creating portions of tissue thatmay be large enough to form a sufficient amount of graft tissue.

For example, living tissue can be provided with nutrients via adiffusional transport over distances of about 0.1 mm. Accordingly, theexemplary micrografts 120 having at least one dimension that is lessthan about 0.3 mm or, e.g., about 0.2 mm, can exhibit improved viabilityand likelihood to survive, and grow when used in a graft. Such exemplarymicrografts 120 can be better able to receive nutrients (including,e.g., oxygen) when placed in a recipient site, prior torevascularization of the tissue. Larger micrografts 120 can also benefitfrom such diffusional transport of nutrients, and can also be morelikely to survive than significantly larger portions of graft tissue(e.g., conventional full-thickness, split-thickness or meshed grafts).

A fraction of surface tissue removed from the donor site 100 byharvesting (which can correspond to a fractional surface area of theexemplary donor site 100 occupied by the holes 110) may be less thanabout 70%, or more preferably less than about 50%. The fraction oftissue removed can be sufficiently large to provide enough harvestedmicrografts 120 to form a graft therefrom of appropriate size, but smallenough to facilitate rapid healing at the donor site 100 based on growthfrom the remaining undamaged tissue. Other fractions of tissue can beremoved from a donor site 100 depending on factors such as, e.g., theparticular characteristics of the donor site 100, the size of the graftneeded, and the overall amount of donor site tissue available.

In further exemplary embodiments of the present disclosure, a graft 200can be provided by embedding or inserting a plurality of micrografts 120in a biocompatible matrix 210 as shown, e.g., in FIG. 2A. The exemplarymatrix 210 containing the micrografts 120 can be exposed to nutrients topromote growth of the harvested micrografts 120, e.g., to form acontinuous or nearly continuous layer of tissue in the graft 200 aftergrowth has occurred. The exemplary graft 200, which can include thematrix 210 and the micrografts 120, may be placed directly over arecipient site 220 (e.g., a cleaned wound area) as shown in FIG. 2B. Theexemplary micrografts 120 can also include stern cells as describedherein, which can also facilitate healing and integration of theexemplary micrografts 120 when they are transplanted to the recipientsite 220. The recipient site 220 can provide nutrients and/or promoterevascularization of the harvested micrografts 120, which can furtherenhance their growth through the matrix 210 to eventually fill in thespaces separating them. For example, FIG. 2B shows the micrografts 120after they have begun to grow into the surrounding matrix 210.

In one exemplary embodiment, the micrografts 120 can be placed in thematrix 210 at approximately the same spacing (e.g., a similar arealdensity) as they were removed from the donor site 100. This exemplaryconfiguration can generate an amount of graft tissue that may beapproximately the same size as the overall harvested area of the donorsite 100 after the micrografts 120 grow and fill in the spaces betweenthem with new tissue. The average spacing of the micrografts 120 in thematrix 210 can also be increased to form a graft tissue that is largerthan the overall area of the harvested donor site 100. The particularspacing of the micrografts 120 in a particular graft 200 can be selectedbased on factors such as, e.g., the size and fractional damage of thedonor site 100, the size of the recipient site 220 to be covered by theskin graft 200, the time needed for the micrografts 120 to regrow andform a continuous tissue layer, the desired appearance of the graftedrecipient site, etc. For example, the exemplary micrografts 120 can bespaced far apart in a particular graft, which can provide a larger graftarea hut can also require longer healing time and the possibility ofsome visible scarring or texture in the healed graft 200.

In a further exemplary embodiment, tissue portions 320 such as thatshown in FIG. 3C can be harvested in an elongated, narrow strip-likeshape. One or more of the exemplary tissue strips 320 can include bothepidermal tissue 130 as well as dermal tissue 140, which can be similarto the micrograft 120 shown in FIG. 1C. For example, the height of theexemplary tissue strip 320 may be about 3 mm, or another length that maycorrespond to a local depth of the dermal layer at the donor site 100.Larger and/or smaller depths can also be selected when harvesting tissuestrips 320 based on, e.g., characteristics of the donor and recipientsites, the wound to be repaired by grafting, etc.

Harvesting of such exemplary tissue strips 320 can leave long, narrowgrooves 310 in a donor region 100 as shown, e.g., in FIG. 3A. A width ofthe grooves 310 (and thus a width of the harvested tissue strips 320)can be less than about 1 mm, or less than about 0.5 mm. In certainexemplary embodiments, the width of such tissue strips can be less thanabout 0.3 mm, or about 0.2 mm. As described herein, such a smalldimension can facilitate diffusional transport of nutrients to the grafttissue and can improve viability of the harvested tissue. A depth of thegrooves 310 from the skin surface can correspond to the height of theharvested strips 320.

A surface area fraction of the exemplary donor site 310 that is removedto form tissue strips 320 can be less than about 70%, or about 50% orless. Factors governing a selection of parameters associated with theharvested elongated tissue strips 320 (e.g., widths and area fractionsremoved from the donor site) my be similar to those described above withrespect to the substantially cylindrical micrografts 120. The length ofthe harvested strips 320 can be selected based on factors such as, forexample, ease of cutting, removing, and handling the thin tissue strips320, the size of the donor site 100, etc. The elongated grooves 310formed in the donor site can may also be able to heal rapidly withlittle or no visible scarring as shown in FIG. 3B, because of the smalllateral dimension and presence of adjacent healthy tissue that cansupport local tissue regrowth.

The harvested strips 320 can be placed, e.g., in a biocompatible matrixsimilar to the matrix 210 shown in FIG. 2A. The tissue strips 320 can bearranged in an approximately parallel configuration, e.g., correspondingto the configuration of the donor-site grooves 310 from which they wereremoved. The spacing between the strips 320 can alternatively beincreased or decreased relative to the spacing of the grooves 310 in thedonor site 100 as desired, e.g., to provide either larger overall areasof graft tissue or more densely packed graft tissue, respectively. Suchharvested tissue strips 320 can be used for certain grafting proceduresbecause the long dimension can preserve structures in the harvested skintissue that may promote revascularization and improve healing of thegraft formed therefrom.

Harvested tissue portions can be removed from the donor site in othershapes, including tile patterns or fractal-like shapes. In general, eachremoved piece of tissue (and, e.g., each corresponding hole or void inthe donor site) can have at least one small dimension that is less thanabout 1 mm, or less than 0.5 mm. In certain exemplary embodiments, thissmall dimension can be less than about 0.3 mm, or about 0.2 mm.

In further exemplary embodiments, the harvested tissue portions can beplaced at the recipient site in a dense configuration. For example, FIG.4A is a schematic top view of a plurality of substantially cylindricalmicrografts 120 that can be gathered in an exemplary dense arrangement,e.g., where adjacent ones of the exemplary micrografts 120 are in atleast partially direct contact each other. FIG. 4B is a schematic sideview of the micrografts 120 shown in FIG. 4A. This exemplary denseconfiguration can provide a graft that is smaller than the overall areaof the harvested donor site 100, hut which can tend to heal faster andbe less likely to produce visible scarring than grafts formed usingspaced-apart harvested tissue portions 120, 320. Similar exemplary denseconfigurations of harvested tissue can be formed using, e.g., elongatedstrips of tissue 320 shown in FIG. 3C or the like.

The exemplary biocompatible matrix 210 can be formed using one or morematerials structured to provides mechanical stability and/or support tothe harvested micrografts 200, and/or which may promote tissue regrowth.Examples of materials which can be used to form the matrix 210 caninclude polylactic acid (PIA), collagen, or hyaluronic acid (e.g.,hyaluranon). Nutrients or other additives can also be provided in thematrix 210 to further promote tissue regrowth. Red or near-infraredlight can also be used to illuminate the donor site and/or the recipientsite after tissue harvesting and placement of the graft tissue tofurther promote healing of the tissue.

In certain exemplary embodiments, techniques such as photochemicaltissue bonding can be used to improve mechanical stability of themicrografts 120 and/or tissue strips 320 in the matrix 210. For example,a technique for photochemical tissue bonding is described in U.S. Pat.No. 7,073,514). This technique includes an application of aphotosensitizer to a tissue, followed by irradiation withelectromagnetic energy to produce a tissue seal. For example, aphotosensitizer such as Rose Bengal can be applied to the matrix 210containing the exemplary micrografts 120 and/or tissue strips 320,followed by exposure of the matrix to green light for about two minutes.Photochemical tissue bonding can catalyze a polymerization reactionwhich may facilitate a stronger bonding of the micrografts 120 and/ortissue strips 320 to the matrix 210, where the matrix 210 can include aprotein such as, e.g., hyaluronic acid or collagen.

In further exemplary embodiments of the present disclosure, an apparatus500 can be provided, such as that shown in FIG. 5A, which can facilitateharvesting of the exemplary micrografts 120 from the donor site 100 asdescribed herein. The exemplary apparatus 500 can include a hollow tube510 that can be formed of metal or another structurally rigid material.For example, the tube 510 can be formed using a stainless steel, abiopsy needle, or a similar structure. The tube 510 can be coated with alubricant or low-friction material, such as Teflon®, to furtherfacilitate the passage of the tubes 510 through the donor site tissue100.

The inner diameter of the tube 510 can be selected to approximatelycorrespond to a particular diameter of a micrograft 120 to be removedfrom the donor site 100 as described herein. For example, 18 or 20 gaugebiopsy needles (e.g., having an inner diameter of 0.838 mm and 0.564 mm,respectively) or the like can be used to form the tube. A biopsy tubehaving a larger gauge (and smaller inner diameter) can also be used. Awidth or diameter of the harvested micrograft 120 can be slightlysmaller than the inside diameter of the apparatus 500 used to harvestit.

A distal end of the tube 510 can be shaped to form a plurality of points520. For example, the two exemplary points or extensions 520 shown inFIG. 5A can be formed by grinding opposite sides of the tube 510 at anangle relative to the long axis of the tube 510. In a further exemplaryembodiment as shown in FIG. 5B, an exemplary apparatus 550 can beprovided that includes a tube 510 with three points or extensions 520provided at a distal end thereof. This exemplary configuration can beformed, e.g., by grinding 3 portions of the tube 519 at an anglerelative to the long axis thereof, where the three portions can bespaced apart by about 120 degrees around the perimeter of the tube 510.In still further exemplary embodiments, an apparatus can be provided forharvesting micrografts that includes a tube having more than threepoints or extensions 520 provided at a distal end thereof, e.g., a tube510 having four, five, six, seven or eight points 520.

The exemplary points or extensions 520 can facilitate insertion of theapparatus 500, 550 into tissue at the donor site 100. The exemplarypoints or extensions 520 that are formed, e.g., by grinding portions ofthe distal end of the tube 510 can also have a beveled edge along theirsides, which can further facilitate insertion of the apparatus 500, 550into donor-site tissue.

The exemplary apparatus 500 can also included a collar or stop 540provided on an outer surface of the tube 510. The exemplary stop 540 canbe affixed to the tube 510 at a particular distance from the ends of thetips 520, or this distance may be adjustable, e.g., over a range oflengths by moving the stop 540 along the axis of the tube 510.

FIG. 6A illustrates the exemplary apparatus 500 after it is insertedinto the tissue at the donor situ 100, e.g., until the stop 540 contactsthe surface of the donor site 100. A portion of tissue 600 can bepresent within a lower portion of the tube 510. Lateral sides of thistissue portion 600 can be cut or severed from the surrounding tissue bythe distal end of the tube 510 and/or points 520 as the tube 510penetrates into the donor site tissue 100. Such tissue 600 can remainwithin the tube 510, and be separated from the donor site 100 to formthe micrograft 120, e.g., when the tube 510 is removed from the donorsite 100 as shown in FIG. 6B. The exemplary micrograft 120 thus formedcan include both epidermal tissue 130 and dermal tissue 140.

The exemplary micrograft 120 can be removed from the apparatus, e.g., byproviding pressure through an opening 620 at a proximal end of the tube510 as shown, e.g., in FIG. 6C. Such pressure can be provided, e.g., byblowing into the opening, by squeezing a flexible bulb attached thereto,by opening a valve leading from a source of elevated pressure such as asmall pump, etc. Alternatively, the exemplary micrografts 120 can beharvested by insetting the exemplary apparatus 500 into a plurality oflocations of the donor site 100. Each micrograft 120 within the tube 510can then push any micrografts above it towards the opening 620. Once thetube 520 has been filled with the harvested tissue, each additionalinsertion of the exemplary apparatus 500 into the donor site 100 canfacilitate pushing of an uppermost micrograft 120 within the tube 510out of the proximal opening 620.

The exemplary apparatus 500 can be inserted into the donor site tissue100 to a depth corresponding approximately to a desired length of theharvested micrografts 120. Such distance can be determined and/orcontrolled, e.g., by appropriate placement or adjustment of the stop 540on the exemplary apparatus 500. For example, the exemplary apparatus 500can be configured or structured such that the points or extensions 520extend to a location at or proximal to the dermal/fatty layer junction610 as shown in FIG. 6A. For example, the micrograft 120 can be removedfrom the donor site 100 by removing the apparatus 500 from the donorsite without rotating the tube 510 around the axis thereof. In contrast,conventional biopsy needles and the like may require a rotation aroundthe long axis to facilitate removal of tissue samples from thesurrounding tissue. The points or extensions 520 provided on theexemplary apparatus 500 can facilitate such removal of the micrograft120 from the surrounding tissue at the donor site 100.

In certain exemplary embodiments, some or all of the tissue at the donorsite can be cooled, frozen, or partially frozen prior to harvesting themicrografts 120. Such freezing can facilitate cutting, removal,handling, and/or viability of the micrografts 120. The donor site tissue100 can be cooled or frozen using conventional cooling techniques suchas, e.g., applying a crypspray or contacting a surface of the donor site100 with a cooled object for an appropriate duration. The exemplaryapparatus 500 can also be cooled prior to harvesting the micrografts120. Such cooling and/or freezing can, e.g., increase a mechanicalstability of the micrografts 120 when they are harvested and/or placedin the matrix 210.

The exemplary micrografts 120 can be provided into the matrix 210 usingvarious techniques. For example, the individual micrografts 120 can beinserted into particular locations of the matrix 210 using, e.g.,tweezers or the like. The exemplary apparatus 500 containing a harvestedmicrograft 120, as shown in FIG. 6B, can also be inserted into alocation of the matrix 210, and pressure can be applied to the proximalopening 620 to push the micrograft 120 into the matrix 210. Theexemplary apparatus 500 can then be removed from the matrix 210, and theprocedure repeated to place a plurality of micrografts 120 in the matrix210. The proximal opening 620 can be covered while the apparatus 500 isbeing inserted into the matrix 210 to prevent the micrograft 120 frombeing pushed further up into the apparatus 500. For example, the upperportion of the tube 510 can be filled with a fluid, e.g., water or asaline solution, to provide an incompressible volume that can furtherprevent the micrograft 120 from rising further up into the tube 510.Such fluid can also facilitate a removal of the micrograft 120 from theexemplary apparatus 500 by providing pressure at the proximal opening620.

Exemplary procedures for harvesting and implanting the micrografts 120described herein can be used to provide the micrografts 120 directlyinto, e.g., substantially whole tissue at the recipient site. Forexample, the micrografts 120 can be harvested from the donor site 100that can contain melanocytes, and inserted directly into tissue at arecipient site that lacks sufficient melanocytes. Such exemplaryprocedure can be used to recipient skin tissue, e.g., to treat vitiligoor similar conditions. Tissue at the recipient site can also be frozenor partially frozen, as described herein, prior to the insertion of themicrografts 120 therein.

The exemplary micrografts 120 can also be harvested from a healthy donorsite and placed directly into scar tissue to facilitate growth ofhealthy tissue in the scar. Optionally, portions of tissue can beremoved from the recipient site prior to placing micrografts in holes atthe recipient site that are formed by the removal of these tissueportions. The holes can be about the same size or slightly larger thanthe size of the micrografts 120 to be inserted therein, to facilitatesuch insertion. The holes can be formed at the recipient site, e.g.,using one or more of the tubes 510 as described herein, by removing orablating the tissue using, e.g., an ablative laser, etc.

In a further exemplary embodiment of the present disclosure, anexemplary apparatus 700 can be provided as shown in FIG. 7. Theapparatus 700 can include, e.g., a plurality of tubes 510 affixed ormechanically coupled to a base 710. The tubes 510 can be provided invarious configurations, e.g., in a linear array, or in any one ofvarious two-dimensional patterns along the base 710. The number of tubes510 provided in the exemplary apparatus 700 can be, for example, greaterthan five tubes 510, more than about 10 tubes, or more than about 30tubes 510.

An enclosure 720 may be provided in communication with proximal openings620 of the tubes 510. The enclosure 720 can also be provided incommunication, e.g., with a pressure source 730. For example, thepressure source 730 can include a pump or a deformable bulb or the like.The pressure source 730 can include, e.g., a flexible membrane providedin communication with the enclosure 720, such that an elevated pressurecan be provided within the enclosure 720 when the membrane is deformed.Such configurations can facilitate applying pressure to the proximalopenings 620 for removal and/or insertion of the micrografts 120 thatcan be harvested in the tubes 510, as described herein.

A vibrating arrangement 740 may optionally be provided in the apparatus700. The vibrating arrangement 740 can be mechanically coupled to thebase 710 and/or the tubes 510 to facilitate the insertion of the tubes510 into the tissue or matrix material for harvesting or placement ofmicrografts 120. The vibrating arrangement 740 can have an amplitude ofvibration in the range of about 50-500 μm, or between about 100-200 μm.The frequency of the induced vibrations can be between about 10 Hz andabout 10 kHz, or between about 500 Hz and about 2 kHz, or even about 1kHz. Particular vibration parameters can be selected based on, e.g., thesize, average spacing, and material of the tubes 510, the number oftubes 510 in the exemplary apparatus 700, and/or the tissue beingtreated. The vibrating arrangement 740 can include circuitry configuredto adjust the amplitude and/or frequency of the vibrations.

The exemplary apparatus 700 can be used to simultaneously obtain aplurality of the micrografts 120 in the plurality of the tubes 510.Exemplary procedures for obtaining and removing such micrografts 120using the exemplary apparatus 700 can be similar to the proceduresdescribed herein for obtaining single micrografts 120 using theexemplary apparatus 500 shown in FIGS. 6A-6C.

The vibration can also assist in severing tissue proximal to the distalend of the tubes 510 after they are fully inserted into the donor site100. This can facilitate separation and/or extraction of the tissueportions within the tubes 510 from the donor site s100. These tissueportions can also be held by friction within the tubes 510 as the tubes510 are withdrawn from the donor site 100.

In further embodiments, the donor site tissue can be pre-cooled prior toinsertion of the tubes 510, e.g., using convective or conductivetechniques such as applying a cryospray or contacting the tissue surfacewith a cooled object. Cooling of the donor site 100 can reduce asensation of pain when the tubes 510 are inserted into the donor sitetissue 100, and can also make the tissue 100 more rigid and facilitate amore accurate severing of tissue portions (e.g., micrografts 120) by thetubes 510.

The positions and spacing of the tubes 510 in the exemplary apparatus700 can be determined, e.g., based on characteristics of the micrografts120 to be obtained, a damage pattern to the donor site 100, and/or otherfactors as described herein above. The number of the tubes 510 providedin the exemplary apparatus 700 can be selected based on various factors.For example, a larger number of tubes 510 may be desirable to allow moremicrografts 120 to be harvested simultaneously from a donor site 100.Such exemplary configuration can facilitate a more efficient harvestingprocess. A smaller number of the tubes 510 can be easier to insertsimultaneously into the donor site tissue 100. Further, the exemplaryapparatus 500 having a very large number of the tubes 510 can bedifficult to manufacture and/or maintain.

The harvested tissue portions can be deposited directly from the tubes510 into the biocompatible matrix material 210. The tubes 510 and tissueportions contained therein can be cooled before removal of the tissueportions. This can stiffen the tissue portions within the tubes 510 andmake them easier to manipulate and position.

In a further embodiment, an apparatus can be provided that includes aplurality of substantially parallel blades. The ends of certain ones ofthe adjacent blades can be connected or closed off to provide, e.g.,narrow rectangular openings between adjacent blades. Such an exemplaryapparatus can be used, e.g., to form the tissue strips 320 such as thatshown in FIG. 3C. Spacings, lengths, and other features of thisexemplary apparatus can be selected based on factors similar to thosedescribed herein, e.g., for the exemplary apparati 500, 700.

In further exemplary embodiments of the present disclosure, theexemplary methods and apparati described herein can be applied to othertissues besides skin tissue, e.g., internal organs such a s a liver orheart, and the like. Thus, grafts can be formed for a variety of tissueswhile producing little damage to a donor site and facilitating rapidhealing thereof, while creating graft tissue suitable for placement atrecipient sites.

EXAMPLE

An image of a distal end of an exemplary apparatus that includes twopoints is shown in FIG. 8A. This apparatus is similar to the exemplaryapparatus 500 illustrated, e.g., in FIG. 5A. A further rotated image ofthis exemplary apparatus is shown in FIG. 8B. The exemplary apparatuswas formed using a tube having an outside diameter of about 1 mm, and aninside diameter of about 0.5 mm. The points or extensions were formed bygrinding two opposite sides of the distal end of the tube at anappropriate angle relative to the axis of the tube. The angle used wasabout 30 degrees, although other angles may also be used. A beveled edgeof the tube wall can be seen along the sides of the points orextensions. The shape of these points can facilitate insertion of theapparatus into tissue of a donor site and/or separation of a portion ofmicrograft tissue from the donor site, as described in more detailherein. For example, such micrografts can be separated and removed fromthe donor site by inserting and withdrawing the apparatus from the donorsite tissue without rotating the tube along its axis.

FIG. 9 is an image of a plurality of micrografts obtained from a donorsite of ex vivo skin tissue using the apparatus shown in FIGS. 8A-8B.The micrografts are elongated and substantially similar in shape,although details of the shapes my be somewhat irregular. An upperportion of these micrografts includes epidermal tissue, and the lowerportion of these micrografts include dermal tissue removed from thedonor site. The width of these micrografts is slightly smaller than theinternal diameter of the tube shown in FIGS. 5A-8B that was used toharvest them.

The micrografts shown in FIG. 9 were removed from the apparatus byinserting the exemplary apparatus into donor site a plurality of times,until the tube was filled with harvested tissue. Each subsequentinsertion of the apparatus into the donor site tissue then forced theuppermost micrograft out of the proximal end of the tube, where it wasretrieved individually for analysis. Such micrografts can also beremoved by applying pressure to the proximal end of the tube containingthe micrograft, to force it out of the distal end of the tube asdescribed herein.

The foregoing merely illustrates the principles of the presentdisclosure. Various modifications and alterations to the describedembodiments will be apparent to those skilled in the art in view of theteachings herein. It will thus be appreciated that those skilled in theart will be able to devise numerous techniques which, although notexplicitly described herein, embody the principles of the presentdisclosure and are thus within the spirit and scope of the presentdisclosure. All patents and publications cited herein are incorporatedherein by reference in their entireties.

1-33. (canceled)
 34. An apparatus for obtaining skin micrografts from adonor site, the apparatus comprising: a plurality of hollow tubes, eachof the plurality of hollow tubes comprising: at least two pointsdisposed at a distal end thereof; a bevel disposed between the at leasttwo points, the at least two points and the bevel configured to severand capture a corresponding skin micrograft upon insertion of therespective hollow tube into the donor site; and an inner diameter of 1millimeter or less configured to retain the skin micrograft uponwithdrawal of the respective hollow tube from the donor site; and a baseconfigured to secure the plurality of hollow tubes, such that the distalends of the plurality of hollow tubes are aligned during insertion intothe donor site.
 35. The apparatus of claim 34, wherein the at least twopoints are angled thirty degrees relative to a center axis of the hollowtube.
 36. The apparatus of claim 34, further comprising a stop connectedto the plurality of hollow tubes and disposed at a fixed distance fromthe distal ends of the plurality of hollow tubes.
 37. The apparatus ofclaim 36, wherein the fixed distance from the distal ends corresponds toan approximate dermal layer depth of the donor site.
 38. The apparatusof claim 36, wherein the fixed distance from the distal ends correspondsto an approximate stem cell depth of the donor site.
 39. The apparatusof claim 36, wherein the fixed distance from the distal ends correspondsto a skin micrograft including at least one melanocyte.
 40. Theapparatus of claim 34, wherein the plurality of hollow tubes are affixedto the base such that the skin micrografts are individually retainedwithin the plurality of hollow tubes.
 41. The apparatus of claim 34,wherein a contact friction between the skin micrograft and the hollowtube retains the skin micrograft within the hollow tube upon withdrawalfrom the donor site.
 42. The apparatus of claim 34, wherein theplurality of hollow tubes are a fixed distance from one another, suchthat the captured skin micrografts comprise less than 50% of the donorsite.
 43. The apparatus of claim 34, further comprising a vibratingarrangement in contact with the base, and configured to vibrate theplurality of hollow tubes to facilitate the insertion into the donorsite.
 44. The apparatus of claim 43, wherein the vibrating arrangementhas an amplitude of vibration of between 50 μm and 500 μm, and afrequency of vibrations between 10 Hz and 10 kHz.
 45. The apparatus ofclaim 44, wherein the vibrating arrangement includes circuitryconfigured to adjust the amplitude and frequency of the vibrations. 46.An apparatus for obtaining skin micrografts, the apparatus comprising: aplurality of hollow tubes, each of the plurality of hollow tubescomprising: at least two points disposed at a distal end thereof andconfigured to sever and capture a corresponding skin micrograft uponinsertion of the respective hollow tube into an epidermis; and an innerdiameter of 1 millimeter or less configured to retain the skinmicrograft upon withdrawal of the respective hollow tube from theepidermis; a base affixed to the plurality of hollow tubes, such thatthe distal ends of the plurality of hollow tubes are aligned duringinsertion into the epidermis; and a vibrating arrangement in contactwith the base, and configured to vibrate the plurality of hollow tubesto facilitate the insertion into the epidermis.
 47. The apparatus ofclaim 46, wherein the vibrating arrangement has an amplitude ofvibration of between 50 μm and 500 μm, and a frequency of vibrationsbetween 10 Hz and 10 kHz.
 48. The apparatus of claim 47, wherein thefrequency of vibrations is between 500 Hz and 2 kHz.
 49. The apparatusof claim 47, wherein the amplitude of vibration is between 100 μm and200 μm.
 50. The apparatus of claim 46, wherein the vibrating arrangementincludes circuitry configured to adjust amplitude and frequency ofvibrations.
 51. The apparatus of claim 46, wherein the at least twopoints are angled 30 degrees relative to a center axis of the hollowtube.
 52. The apparatus of claim 46, wherein the plurality of hollowtubes are aligned and affixed to the base such that the skin micrograftsare individually retained within the plurality of hollow tubes.
 53. Theapparatus of claim 46, wherein the vibrating arrangement is configuredto vibrate after insertion of the plurality of hollow tubes to ensureseverance of the skin micrografts.